The City, the County of Sonoma and Sonoma County Water Agency (the City’s copermitees under the NPDES storm water permit), monitor water quality to assess local creeks and focus on local pollutants of concern including elevated temperatures, sediment, and bacteria.  Monitoring includes chemical and biological sampling during storm events and the low flow season.  Chemical monitoring provides concentrations of constituents while biological tests show the response of actual living organisms to creek samples or conditions.

 Chemical Monitoring

• Measure specific constituents at two locations on Santa Rosa Creek during winter storms to develop trends and assess the impact of urban runoff to the creek.


• Measure specific constituents at two storm drain outfalls (Colgan and Piner Creeks) during winter storms to characterize urban runoff from different land uses.


• Deploy remote temperature loggers during the summer to record hourly stream temperature in Brush, Colgan, Paulin, and Santa Rosa Creeks.

 Biological Monitoring

• Perform bioassays with Rainbow trout and Ceriodaphnia (water fleas) to assess the survival of these species in water samples collected from Brush, Colgan, Matanzas, Paulin, Peterson, Piner, and Santa Rosa Creeks.


• Conduct bioassessments during low flow conditions by collecting aquatic macroinvertebrates (insects and bugs) from streambeds and identifying them from Brush, Colgan, Matanzas, Paulin, Peterson, and Piner Creeks.  Based on the types and abundance of different invertebrates, water quality and habitat condition can be scored.  The assessments also include a detailed habitat survey to characterize the overall stream condition.  For more information on the how Santa Rosa’s high school students use bioassessments to study local creeks.  High School Students Study Healthy Creeks

Review the most recent NPDES Permit Annual Report for sampling results.

If abnormal testing results or unusual field conditions are observed, then a follow up investigation is launched to determine what is causing the condition.  Enforcement can occur if an illicit discharge is discovered or outreach can be focused to address practices that cause impacts to water quality or creek habitat.